Electrostatic chuck sidewall gas curtain

ABSTRACT

The present disclosure describes an apparatus. The apparatus includes a chuck for placing an object thereon, a gas passage extending along a periphery of an outer sidewall of the chuck and separating the chuck into an inner portion and a sidewall portion, and a plurality of gas holes through the sidewall portion and configured to connect a gas external to the chuck to the gas passage.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 16/445,336, titled “Electrostatic Chuck SidewallGas Curtain,” filed on Jun. 19. 2019, which claims the benefit of U.S.Provisional Patent Application No. 62/692,128, titled “Novel ESCSidewall Air Curtain For Arcing Prevention,” filed on Jun. 29, 2018, allof which are incorporated herein by reference in their entireties.

BACKGROUND

Electrostatic chucks (ESCs) are widely used in various semiconductorprocesses to hold a wafer during different operations, such asplasma-based etching, ion implantation, chemical vapor deposition (CVD),etc. An ESC includes a platen with integral electrodes. These electrodesare biased with a high voltage during operation to establish anelectrostatic holding force between the platen and the object being held(e.g., the wafer). The portion of the ESC that provides theelectrostatic holding force is referred to as a “chuck.”

ESCs can be used in different systems, e.g., etching, ion implantation,and CVD systems. For example, in a dry etch system, an ESC is located ina chamber to hold the wafer to be etched. Reactive gases can be flowninto the chamber and plasma can be generated over the wafer.Radicals/high-energy ions can be formed from the plasma and strike thewafer surface. The radicals/high-energy ions can collide with the wafersurface and remove portions of the wafer by knocking off and reactingwith the material.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the common practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofillustration and discussion.

FIG. 1 illustrates a cross-sectional view of an electrostatic chuck.

FIGS. 2A and 3A each illustrates a cross-sectional view of anelectrostatic chuck structure, according to some embodiments of thepresent disclosure.

FIG. 2B is a top view of the electrostatic chuck structure illustratedin FIG. 2A along the 2-2′ direction.

FIG. 3B is a top view of the electrostatic chuck structure illustratedin FIG. 3A along the 3-3′ direction.

FIG. 4 illustrates a control system, according to some embodiments ofthe present disclosure.

FIG. 5 illustrates a method for protecting an electrostatic chuckstructure from damage by deflected radicals, according to someembodiments of the present disclosure.

FIG. 6 illustrates an exemplary computer system for implementing variousembodiments of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are merely examples andare not intended to be limiting. In addition, the present disclosurerepeats reference numerals and/or letters in the various examples. Thisrepetition is for the purpose of simplicity and clarity and, unlessindicated otherwise, does not in itself dictate a relationship betweenthe various embodiments and/or configurations discussed.

In semiconductor fabrication, electrostatic chucks (ESCs) can be used invarious systems, e.g., for holding/fixing, wafers. For example, an ESCcan be used to hold a wafer in a chamber for a dry etch process. Thewafer can be placed over the ESC, and etchant gases can be flown intothe chamber. Under a radio frequency (RF) power, radicals/high-energyions can be formed by ionizing the gas atoms and a plasma can be formedover the wafer. The radicals can bombard the wafer at a high kineticenergy and can remove desired portions of the water.

However, the plasma radicals can also collide with objects positionedadjacent to the ESC (or wafer) and deflect off these objects. Theobjects can be anything, e.g., a part of the chamber or other tools forprocessing the wafer. The deflected radicals can bombard and react withthe outer sidewall of the ESC, causing damage to the ESC over time. Theerosion can impair the outer sidewall (e.g., or the protective coatingover the outer sidewall) of the ESC. The damaged outer sidewall cancause static electricity, which can cause the wafer to bow. As a result,the wafer can be damaged, thus impairing product yield.

FIG. 1 illustrates a wafer-holder structure 100 that carries a wafer Win a chamber for a dry etch process (e.g., wafer-holder structure 100can be housed in a dry etch chamber). Plasma P is formed over wafer W.Wafer-holder structure 100 includes a base 114 and an ESC 110 over base114. ESC 110 includes an electrode 109, a base platen 111, a heatingcomponent 112, and a heat insulating component 113. Electrode 109 can beembedded in base platen 111, and heating component 112 can be embeddedin heat insulating component 113. Wafer-holder structure 100 can providecoulomb force and can attract and hold wafer W during the etch process.Heating component 112 can provide a suitable temperature for the etchprocess. Base 114 can further include a gas tunnel 115 foradjusting/controlling the processing temperature of wafer W. A heattransfer gas can circulate through gas tunnel 115 by flowing into inlet115-1 and flowing out of outlet 115-2 to adjust the surface temperatureof base platen 111. A base bottom 116 can seal the heat transfer gas andseparate inlet 115-1 and outlet 115-2.

During the etch process, etchant gases can be flown into the chamber(e.g., from above wafer P). Under a high RF power, the etchant gases canbe ionized and plasma P can be formed over wafer W. Radicals orhigh-energy ions formed from plasma P can strike the top surface ofwafer P from various directions and react with the materials on the topsurface of wafer W. Because a portion of the radicals can collide withobjects that surround wafer-holder structure 100, the deflected radicals(labeled by arrows 117) can further collide with the outer sidewalls ofESC 110 and/or base 114. The kinetic energy of the radicals and thechemical reaction between the radical and the coating on the outersidewalls can cause erosion to the coating over time. The loss ofcoating due to erosion can generate static electricity, which can causewafer W to bow, thus resulting in a damaged wafer and lower yield.

The present disclosure provides an ESC structure and a method to preventor reduce damage/erosion on the coating of an ESC's outer sidewallcaused by radicals. The disclosed ESC structure employs a gas curtain tosurround its outer sidewall, thus forming a barrier for the deflectedradicals. The gas curtain prevents or reduces the amount of deflectedradicals that reaches the ESC's outer sidewall, thus preventing orreducing erosion caused by the bombardment of the deflected radicals andthe chemical reaction between the deflected radicals and the coating onthe ESC's outer sidewall. The gas curtain can be formed by various ways,e.g., by forming gas passages along the periphery of the ESC structureand gas holes that connect the gas passages to a background gas externalto the ESC structure and by flowing an inert gas into the gas passage.The background gas can include any gas (e.g., gas for chemical reaction,carrier gas, and plasma-generating gas) in the chamber where the ESCstructure is located. The inert gas that exits from the gas holes canform a gas curtain that surrounds the ESC structure to prevent or reducethe deflected radicals from reaching the outer sidewall of the ESCstructure. Because the inert gas is chemically stable during the dryetch, the etching of the wafer would not be affected by the gas curtain.The ESC structure is thus less susceptible to sidewall damage caused byplasma-based etching. Also, the wafer can be less susceptible to bowingcaused by static electricity.

FIGS. 2A and 2B illustrate a wafer-holder structure, according to someembodiments. FIG. 2A illustrates a cross-sectional view 200 of thewafer-holder structure along the x-z plane, and FIG. 29 illustrates atop view 250 of the wafer-holder structure (along the 2-2′ direction)along the x-y plane. The wafer-holder structure can include an ESCstructure 210 and a base structure 214. Wafer W can be placed over ESCstructure 210. ESC structure 210 can include a base platen 211, anelectrode 209 embedded in base platen 211, a heat insulating component213, and a heating component 212 embedded in heat insulating component213. ESC structure 210 can be fixed on base structure 214. Basestructure 214 can include a cooling component for adjusting thetemperature of base platen 211, where wafer W is placed. In someembodiments, the cooling component includes a gas tunnel 215 that allowsa heat transfer gas (e.g., helium gas) to circulate through inlet 215-1and outlet 215-2. The arrows at inlet 215-1 and outlet 215-2 indicatethe directions of the gas flow. In some embodiments, base structure 214includes a bottom portion 216 that seals gas tunnel 215 between inlet215-1 and outlet 215-2. Other structures/devices between ESC structure210 and base structure 214 are not shown in the figures for simplicity.In some embodiments, the wafer-holder structure exhibited in FIGS. 2Aand 2B can be housed in a chamber (e.g., a dry etch chamber).

Base platen 211 can have a mounting surface Where an object (e.g., waferW) can be attracted to and placed on. Base platen 211 can include asuitable insulating material, such as aluminum oxide (Al₂O₃/alumina)and/or aluminum nitride (AlN). Base platen 211 can have any suitabledimensions. For example, base platen 211 can have a thickness of about 1μm to about 30 μm along the z axis, and the diameter of base platen 211can be about 6 inches, about 8 inches, or other values suitable to holdwafers to be processed.

Electrode 209 can be in the shape of a thin film, embedded in baseplaten 211. Electrode 209 can have a monopolar shape or a bipolar shape.Electrode 209 can be connected to a power supply (inside or outside ofthe wafer-holder structure, not shown in the figures) so that a voltagecan be applied to electrode 209 by the power supply. Coulomb force canbe generated between ESC structure 210 and wafer W. Wafer W can then beattracted on the mounting surface of base platen 211. The magnitude ofthe voltage can be proportional to the coulomb force that attracts waferW. Electrode 209 can include a suitable conductive material, such astungsten, molybdenum, etc.

Heat generating component 212 can be connected to a power supply (insideor outside of wafer-holder structure, not shown in the figures) togenerate heat when a voltage is applied to heat generating component212. Heat generating component 212 can heat base platen 211 to a desiredtemperature, e.g., between about 100 degrees Celsius and about 300degrees Celsius. Heat generating component 212 can include suitablematerials of sufficiently low specific heat capacity, such as metalscopper (Cu), tungsten (W), and/or nickel (Ni)). Heat generatingcomponent 212 can be uniformly distributed in heat insulating component213 and have suitable dimensions. For example, heat generating component212 can have a thickness of about 5 μm to about 100 μm.

Heat insulating component 213 can include an insulating material tocover heat generating component 212. Heat insulating component 213 caninclude a suitable insulating material, such as an insulating resin(e.g., polyimide, low-melting-point glass, alumina and/or silica). Athermal expansion coefficient of heat insulating component 213 can besimilar or comparable to a thermal expansion coefficient of base platen211. Heat insulating component 213 can have any suitable length alongthe z axis. For example, heat insulating component 213 can have athickness of about 30 μm to about 1 cm.

Base structure 214 can provide support to ESC structure 210. Basestructure 214 can include materials of sufficient stiffness andcorrosion resistance, such as aluminum. A protection coating, e.g., analumite layer. Base structure 214 can include a cooling component thatcan adjust the temperature of the mounting surface of base platen 211.The cooling component can include a gas tunnel 215. A heat transfer gascan circulate in gas tunnel 215 through inlet 215-1 and outlet 215-2. Abottom portion 216 can seal the heat transfer gas between inlet 215-1and outlet 215-2. The arrows indicate the directions of the gas flow.The heat transfer gas can include any suitable gas, such as helium. Thecooling component can also include gas passages (not shown in thefigures) that connect gas tunnel 215 to the mounting surface of baseplaten 211 (e.g., under wafer W) so the heat transfer gas can cool thesurface temperature of base platen 211, thus adjusting the processingtemperature of wafer W. Optionally, the cooling component can include afluid passage that allows a heat transfer fluid to circulatearound/under heat insulating component 213 and to adjust the surfacetemperature of base platen 211. The fluid can include, e.g., water. Forease of viewing, the fluid passage is not shown in the figures.

ESC structure 210 can include a gas passage 218 under an outer sidewallof ESC structure 210. A plurality of gas holes (or through holes) 220that connect gas passage 218 and a background gas of ESC structure 210can be formed through the outer sidewall. The background gas of ESCstructure 210 can include any gas in a chamber that houses ESC structure210. In some embodiments, the background gas can include any gas that isbetween ESC structure 210 and a chamber that houses ESC structure 210.Gas passage 218 and the plurality of gas holes 220 can allow an inertgas to flow from a gas source and exit from the outer sidewall of ESCstructure 210. The released inert gas can form a gas curtain thatsurrounds ESC structure 210 and prevents deflected radicals fromcolliding with the outer sidewall of ESC structure 210.

As shown in FIGS. 2A and 2B, in some embodiments, gas passage 218 canextend from the bottom of ESC structure 210 and extend vertically (e.g.,along the z axis) to a desired elevation (e.g., a level at which thematerial of the outer sidewall is less susceptible to radicalbombardment and erosion). Gas passage 218 can extend vertically along aperiphery (e.g., under the outer sidewall) of ESC structure 210. Alength of gas passage 218 along the z axis can be sufficiently equal toor smaller than the height of ESC structure 210 along the z axis. Gaspassage 218 can separate (e.g., divide) ESC structure 210 to a sidewallportion 221 (e.g., formed with gas holes 220 and between the backgroundgas and gas passage 218) and an inner portion 223 (e.g., electrode 209,heating component 212, portions of base platen 211 that covers electrode209, and portions of heat insulating component 213 that covers heatingcomponent 212). As shown in FIG. 2B, in some embodiments, gas passage218 surrounds inner portion 223, and sidewall portion 221 surrounds gaspassage 218. The cross-section of inner portion 223 along the x-y planecan have any suitable shape such as a circular shape, a polygonal shape,a square shape, or an irregular shape. As shown in FIG. 2B, in someembodiments, inner portion 223 has a circular shape, gas passage 218 hasa ring shape and surrounds inner portion 223 along the x-y plane, andsidewall portion 221 has a ring shape and surrounds inner portion 223along the x-y plane. Gas holes 220 can be distributed along thedirection that sidewall portion 221 extends in the x-y plane.

Sidewall portion 221 and inner portion 223 can be connected to orseparated from one another. For example, when the height of ESCstructure 210 is equal to the height of gas passage 218 along the zaxis, sidewall portion 221 can be disconnected from inner portion 223.When the height of ESC structure 210 is smaller than the height of gaspassage 218 along the z axis, sidewall portion 221 can be connected toinner portion 223 (e.g., as shown in FIG. 2A). A thickness d3 ofsidewall portion 221 can be in a range of about 0.1 mm to about 0.2 mm.In some embodiments, d3 is about 0.1 mm. A distance d5 between twoadjacent gas holes 220 along the z axis can be in a range of about 0.1mm to about 0.2 mm. In some embodiments, d5 is about 0.1 mm.

Gas passage 218 can surround inner portion 223 of ESC structure 210 fromvarious directions. In some embodiments, gas passage 218 cancontinuously surround inner portion 223 from all directions along thex-y plane, as shown in FIG. 2B. In some embodiments, gas passage 218surrounds a portion of inner portion 223. In some embodiments, gaspassage 218 includes a plurality of gas sub-passages, each surroundinginner portion 223 from a different direction. Each gas sub-passage canbe connected to a same or different inert gas source through a sub-inletof the gas sub-passage. In some embodiments, gas passage 218 is locatedat the side of the outer sidewall that may be the most susceptible toradical erosion. The specific arrangement of gas passages can bedetermined based on, e.g., the distribution/pattern of the radicaldamage and/or design requirements for the ESC structure and should notbe limited by the embodiments of the present disclosure.

In some embodiments, gas passage 218 can also extend along the peripheryof base structure 214. Gas passage 218 can extend horizontally (e.g.,along the x-y plane) and vertically (e.g., along the z axis). In someembodiments, gas passage 218 separates (e.g., divides) base structure214 into a base inner portion (e.g., surrounded by gas passage 218) anda base sidewall portion 222 (e.g., between the background gas and gaspassage 218). In some embodiments, gas holes 220 are formed through basesidewall portion 222. The distribution, pattern, and/or shapes of gasholes 220 formed in base sidewall portion 222 can be the same as orsimilar to the distribution, pattern, and/or shapes of gas holes 220formed in sidewall portion 221 of ESC structure 210.

A plurality of gas holes 220 can be formed connecting gas passage 218and the background gas of ESC structure 210. Gas holes 220 can bedistributed/aligned horizontally (e.g., along the x-y plane) in anysuitable pattern and have horizontal exit directions to allow an inertgas to exit horizontally. In some embodiments, gas holes 220 aredistributed uniformly on the outer sidewall of ESC structure 210. Gasholes 220 can have any suitable shape. In some embodiments, gas holes220 can each have a circular cross-sectional shape along the y-z planeand a diameter d1 of gas hole 220 is in a range of about 0.05 min toabout 0.5 mm. In some embodiments, d1 is about 0.1 mm. A width d2 of gaspassage 218 can be in a range of about 0.1 mm to about 0.2 mm. In someembodiments, width d2 is about 0.1 mm. In some embodiments, ESCstructure 210 has a circular cross-sectional shape along the x-y planeand an arc length d4 between the geometric centers of two adjacent gasholes 220 along the x-y plane is in a range of about 0.1 mm to about 0.2mm. In some embodiments, arc length d4 is about 0.1 mm.

An inert gas can be flown in to gas passage 218 from a gas source,through inlets 219 at the bottom of gas passage 218 and can exit fromgas holes 220. Directions of gas flow of the inert gas are indicated bythe arrows. The inert gas can include any suitable gas that ischemically stable under the processing condition in the chamber. Forexample, the inert gas can include nitrogen. The flow rate of the inertgas can be in a range of about 20 to about 200 standard cubic centimeterper minute (sccm). In some embodiments, the flow rate is about 50 sccm.

The inert gas exiting from gas holes 220 can form a gas curtain alongthe outer sidewall of ESC structure 210. In some embodiments, the atomsof the inert gas in the gas curtain can collide with deflected radicals(not shown in FIG. 2A) and thus form a barrier for the deflectedradicals. Less or no deflected radicals can reach the outer sidewall ofESC structure 210. The outer sidewall of ESC structure 210 is thus lesssusceptible to bombardment and/or erosion of the deflected radicals.

Inlet 219 can be located at any suitable position of gas passage 218 andan inert gas can be flown into gas passage 218 from an inert gas source.For example, inlet 219 can be located at the bottom (e.g., as shown inFIG. 2A) of the wafer-holder structure and/or between the top and thebottom of the wafer-holder structure. Inlet 219 can also include aplurality of sub-inlets for flowing the inert gas into gas passage 218from various directions. The arrangement of inlets 219 can be determinedbased on, e.g., the ease of manufacturing and/or the design requirementof the wafer-holder structure, and should not be limited by theembodiments of the present disclosure.

In some embodiments, gas holes 220 and 222 are distributed uniformlyalong the x-y plane and/or z direction. In some embodiments, thedistribution of gas holes 220 and 222 are based on the damage levels.For example, sidewall portion 221 of ESC structure 210 is moresusceptible to radical damage than the base sidewall portion and canthus be formed with more gas holes 220. In some embodiments, no gaspassage or gas holes are formed in base structure 214.

FIGS. 3A and 3B illustrate another wafer-holder structure, according tosome embodiments. FIG. 3A illustrates a cross-sectional view 300 of thewafer-holder structure along the x-z plane, and FIG. 3B illustrates atop view 350 of the wafer-holder structure along the 3-3′ directionalong the x-y plane. The wafer-holder structure of FIGS. 3A and 3Bincludes a horizontal surface (e.g., along the x axis) and a gas passagethat can be formed under the horizontal surface. Gas holes can be formedthrough the horizontal surface to connect the gas passage to thebackground gas. The horizontal surface can be a part of the ESCstructure or a part of the base. For illustrative purposes, elementslabeled with the same/similar numerals in FIGS. 3A and 3B as in FIGS. 2Aand 2B can be the same or similar, in which the description of theseelements can be found above. Further, the discussion of the wafer-holderstructure in FIGS. 2A and 2B (e.g., benefits of a gas curtain, andbackground gas) can be applied to that in FIGS. 3A and 3B unlessmentioned otherwise. As shown in FIG. 3A, base platen 311 and heatinsulating component 313 can be similar to base platen 211 and heatinsulating component 213, and the cross-sectional area of base platen311 can be different from the cross-sectional area of heat insulatingcomponent 313 along the x-y plane.

in some embodiments, gas passage 318 separates (e.g., divides) ESCstructure 310 into an inner portion 323 and a sidewall portion. As shownin FIGS. 3A and 3B, the sidewall portion of ESC structure 310 caninclude a horizontal sidewall portion 322 (e.g., along the x axis). Insome embodiments, the outer sidewall of ESC structure 310 includeshorizontal sidewall portion 322 and two vertical sidewall portions 324and 325 (e.g., along the z axis) each connected to horizontal sidewallportion 322 at a different end. Vertical sidewall portion 324 can beconnected to horizontal sidewall portion 322 and the top of base platen311. Vertical sidewall portion 325 can be connected to horizontalsidewall portion 322 and the bottom of heat insulating component 313.Gas passage 318 can extend under horizontal sidewall portion 322 and atleast one of vertical sidewall portions 324 and 325. In someembodiments, gas passage 318 extends under horizontal sidewall portion322 and vertical sidewall portions 324 and 325. In some embodiments, gaspassage 318 includes a horizontal passage portion 332 under horizontalsidewall portion 322. Gas passage 318 can include at least one verticalpassage portions connected to horizontal passage portion 332. In someembodiments, gas passage 318 includes two vertical passage portions 334(e.g., under vertical sidewall portion 324) and 335 (e.g., undervertical sidewall portion 325), each connected to horizontal passageportion 332. The total height along the z axis) of vertical passageportions 334 and 335 can be substantially equal to or smaller than thetotal height (e.g., along the z axis) of base platen 211 and heatinsulating component 213. Gas holes 330 can be formed at least throughhorizontal sidewall portion 322, connecting horizontal passage portion332 and the background gas. In some embodiments, gas holes 220 areformed through vertical sidewall portion 221, and/or gas holes 340 areformed through vertical sidewall portion 341. FIG. 3B illustratescross-section view 350 of inner portion 323 along the 3-3′ direction.Inner portion 323 can be similar to or the same as inner portion 223illustrated in FIG. 2B. In some embodiments, inner portion 323 has acircular shape, gas passage 318 has a ring shape and surrounds innerportion 323 along the x-y plane, and vertical sidewall portion 341 has aring shape and surrounds inner portion 323 along the x-y plane,. Gasholes 340 can be distributed along the direction that vertical sidewallportion 341 extends in the x-y plane.

A gas source can be connected to inlet 219 of gas passage 318 to flow aninert gas into gas passage 318. The inert gas can exit from the gasholes 330, 220 and/or 340). Directions of gas flow and positions of thegas curtain are indicated by the arrows. Gas holes 330 can have verticalexit directions to allow the inert gas to exit vertically from gas holes330. In some embodiments, inert gas exiting vertically from gas holes330 can enhance the gas curtain (e.g., surrounding the upper portion,above horizontal sidewall portion 322, of ESC structure 310) exitinghorizontally from gas holes 220 to prevent or reduce deflected radicalsfrom reaching the outer sidewalk of ESC structure 310. In someembodiments, the inert gas exiting from gas holes 340 also forms a gascurtain that surrounds the lower portion (e.g., below horizontalsidewall portion 322) of ESC structure 310.

Horizontal sidewall portion 322 can be coplanar with, above, or underthe interface between base platen 211 and heat insulating component 313.Horizontal sidewall portion 322 can have a suitable dimension.Horizontal sidewall portion 322 can be formed by the dimensiondifference between adjacent layers/structures, e.g., base platen 311 andheat insulating component 313 along the x-y plane or between insulatingcomponent 313 and base structure 214 along the x-y plane. The pattern,shape, and distribution of gas holes 220, 330, and 340 can be similar toor the same as the pattern, shape, and distribution of gas holes 220 ofFIGS. 2A and 2B.

In some embodiments, gas passage 318 extends through base structure 214.The inert gas is flown into gas passage 318 through inlet 219 located ata bottom of base structure 214. Gas passage 318 can separate (e.g.,divide) base structure 214 into a base sidewall portion (e.g., betweengas passage 318 and the background gas) and a base inner portion (e.g.,surrounded by gas passage 318). Gas holes may or may not be formedthrough the base sidewall portion. In some embodiments, as shown inFIGS. 3A and 3B, gas holes are not formed through the base sidewallportion. Details of passage 318 can be referred to the dimensions ofpassage 218 of FIGS. 2A and 2B.

In some embodiments, the pattern, distribution, dimensions, and/orshapes of the gas passages (e.g., in FIGS. 2A and 2B and FIGS. 3A and3B) are determined based on various factors, such as the shapes anddimensions of the ESC structure and/or the base and the locations of theradical damage. For example, the pattern distribution of gas passage andthe gas holes can be arranged to minimize the radical damage at adesired flow rate of the inert gas.

In some embodiments, the outer sidewall of an ESC structure (or awafer-holder structure) includes sidewall portions that are arranged invarious directions, and a gas passage is formed under one or more of thesidewall portions. In some embodiments, the ESC structure can include afirst sidewall portion in a first direction and a second sidewallportion in a second direction different from the first direction. Eachof the first and the second sidewall portions can have at least one gashole configured to respectively exit the inert gas in the first and thesecond directions to form the gas curtain. The specific shape of the ESCstructure should not be limited by the embodiments of the presentdisclosure.

The gas passage and gas holes can be formed by any suitable method. Insome embodiments, the gas passage is formed by removing a peripheralportion of an ESC to form a sidewall portion and an inner portion. Thesidewall portion and the inner portion can be separated by the gaspassage. The gas holes can be formed by forming through holes in thesidewall portion. In some embodiments, the gas passage is formed bysurrounding an ESC with a suitable material that has sufficientstiffness to block radical bombardment. The gas holes can be formed byforming through holes in the material.

It should be noted that, although the present disclosure describes gasholes with horizontal and/or vertical exit directions, the exitdirections of gas holes can vary in different devices/applications,based on, e.g., the position and the distribution range of the gascurtain. For example, the exit directions of gas holes can be differentfrom the horizontal direction and the vertical direction. In anotherexample, the exit directions of gas holes in a vertical sidewall portionand the exit directions of gas holes in the adjacent horizontal sidewallportion can form angles less than or greater than about 90 degrees inthe x-z plane (e.g., the angles formed by the intersections of the exitdirections in a vertical sidewall portion and exit directions in theadjacent horizontal sidewall portion). The specific exit directions ofgas holes should be determined based on, e.g., the ESC structure, thedesired position and distribution range of the gas curtain, and thechamber pressure, and should not be limited by the embodiments of thepresent disclosure.

FIG. 4 illustrates an system 400 using a wafer-holder structure of thepresent disclosure, according to some embodiments. As shown in FIG. 4 ,system 400 includes a control unit/device 401, a communication means402, a wafer-holder structure 403 with a disclosed ESC structure, and aninert gas 404 flowing into wafer-holder structure 403.

Control unit/device 401 can include any suitable computer system (e.g.,workstation and portable electronic device) to store programs and datafor various operations, such as controlling the processing of a waferplaced over the wafer-holder structure and controlling a flow of inertgas 404 into wafer-holder structure 403. For example, flow rate, chamberpressure, start/end time of inert gas 404, and/or the type of inert gas404 can be controlled by control unit/device 401. In some embodiments,control unit/device 401 includes programs that can determine the flowrate of inert gas 404 based on the power of an etch process. Forexample, a higher flow rate can be used for a higher power, and viceversa. In some embodiments, control unit/device 401 includes programsthat automatically starts flowing inert gas 404 when the power is on. Insome embodiments, control unit/device 401 include programs thatdetermine the type of inert gas 404 to use based on different etchantgases. In some embodiments, control unit/device 401 transmits variouscontrol signals to control the wafer processing and formation of a gascurtain. The different functions of control unit/device 401 should bedetermined based on, e.g., the processing/etching of wafers and/or thechamber condition, and should not be limited by the embodiments of thepresent disclosure.

Communication means 402 can include any suitable network connectionbetween control unit/device 401 and wafer-holder structure 403. Forexample, communication means 402 can include a local area network (LAN)and/or a WiFi network. In some embodiments, control unit/device 401transmits control signals through communication means 402 toadjust/control the flow of inert gas 404 into the gas passage, andcommunication means 402 transmits the control signals to the chambercontaining wafer-holder structure 403.

Wafer-holder structure 403 can be located in a chamber and can includeany wafer-holder structure disclosed by the present disclosure. Thechamber can include any suitable software and/or hardware to receive theimplement the control signals. Wafer-holder structure 403 can include anESC structure. The ESC structure can include a gas passage extending atleast under the outer sidewall that is susceptible to damage caused bydeflected radicals. Gas holes can be formed through the gas passage andconnect the gas passage to the background gas so that an inert gas 404can exit from the gas holes and form a gas curtain around the ESCstructure. The gas curtain can be in the close proximity of the ESCstructure and form a barrier that can prevent the deflected radicalsfrom reaching the outer sidewall of the ESC structure. The flow rate,start/end time of inert gas 404, chamber pressure, and/or the type ofinert gas 404 can be controlled by control unit/device 401.

By using the disclosed ESC structure (or wafer-holder structure), a gascurtain can be formed around the ESC structure and protect the ESCstructure from damage to the outer sidewall caused by deflectedradicals. As a result, wafer bowing due to static electricity can bereduced or prevented. The gas passage and gas holes that form the gascurtain can be used in ESC structures of different shapes anddimensions. Because the inert gas that forms the gas curtain ischemically stable during wafer processing (e.g., etching) and the gascurtain is sufficiently close to the outer sidewall of the ESCstructure, the impact of the gas curtain on wafer processing can beminimized.

FIG. 5 illustrates a method for protecting an electrostatic chuckstructure from damage by deflected radicals, according to someembodiments. In some embodiments, the operations of method 500 can beperformed in a different order. Variations of method 500 are within thescope of the present disclosure.

At operation 501, a wafer can be loaded onto a wafer-holder structure ina chamber. The wafer-holder structure can include any one of thewafer-holder structures of the present disclosure. The wafer-holderstructure can attract and fix the wafer on the mounting surface of thewafer-holder structure.

At operation 502, the wafer can be processed and a gas curtain can beformed to surround the wafer-holder structure. The gas curtain can beformed by flowing an inert gas into the gas passage so that the inertgas can exit from the gas holes. In some embodiments, the processing ofthe wafer is controlled by a control unit/device. Various sensors, suchas a pressure sensor and a temperature sensor, can be used to monitorchamber conditions so the control unit/device can control the waferprocessing on a real-time basis. The control unit/device can controldifferent variables such as the chamber pressure, the flow rate of theetchants, the power applied on the plasma, the processing temperature,etc. Also, the control unit/device flows an inert gas into the gaspassage of the wafer-holder structure during wafer processing (e.g.,after the plasma is formed). The inert gas can exit from the gas holesthat connect the gas passage to the background gas, in which the inertgas forms a gas curtain around the wafer-holder structure. The gascurtain can prevent or reduce deflected radicals (e.g., from the plasmaetching process) from reaching the outer sidewall of the wafer-holdingstructure.

At operation 503, one or more chamber conditions can be controlled andthe flow rate of the inert gas can be adjusted based on the chamberconditions. The control unit/device can monitor the chamber conditions(e.g., chamber pressure) based on feedback information provided bysensors (e.g., temperature and pressure sensors) and adjust the chamberconditions accordingly. For example, if the inert gas causes the chamberpressure to deviate from the predetermined processing parameters, thecontrol unit/device can adjust the flow rate of the inert gas so thatthe chamber pressure reaches the predetermined chamber pressure. In someembodiments, operation 503 can periodically monitor chamber conditionsto ensure that the predetermined processing parameters are achieved.

FIG. 6 is an illustration of an example computer system 600 in whichvarious embodiments of the present disclosure can be implemented,according to some embodiments. Computer system 600 can be used, forexample, in control unit/device 401 of FIG. 4 . Computer system 600 canbe any well-known computer capable of performing the functions andoperations described herein. For example, and without limitation,computer system 600 can be capable of processing and transmittingsignals. Computer system 600 can be used, for example, to control theflowing of inert gas into the gas passage.

Computer system 600 includes one or more processors (also called centralprocessing units, or CPUs), such as a processor 604. Processor 604 isconnected to a communication infrastructure or bus 606. Computer system600 also includes input/output device(s) 603, such as monitors,keyboards, pointing devices, etc., that communicate with communicationinfrastructure or bus 606 through input/output interface(s) 602. Acontrol tool can receive instructions to implement functions andoperations described herein e.g., the functions of system 400 describedin FIG. 4 and the method/process described in FIG. 5 —via input/outputdevice(s) 603. Computer system 600 also includes a main or primarymemory 608, such as random access memory (RAM). Main memory 608 caninclude one or more levels of cache. Main memory 608 has stored thereincontrol logic (e.g., computer software) and/or data. In someembodiments, the control logic (e.g., computer software) and/or data caninclude one or more of the functions described above with respect to thepreviously discussed wafer-holder structure (e.g., wafer-holderstructure 100, 200/250, 300/350, or 403). In some embodiments, processor604 can be configured to execute the control logic stored in main memory608.

Computer system 600 can also include one or more secondary storagedevices or memory 610. Secondary memory 610 can include, for example, ahard disk drive 612 and/or a removable storage device or drive 614.Removable storage drive 614 can be a floppy disk drive, a magnetic tapedrive, a compact disk drive, an optical storage device, tape backupdevice, and/or any other storage device/drive.

Removable storage drive 614 can interact with a removable storage unit618. Removable storage unit 618 includes a computer usable or readablestorage device having stored thereon computer software (control logic)and/or data. Removable storage unit 618 can be a floppy disk, magnetictape, compact disk, DVD, optical storage disk, and/any other computerdata storage device. Removable storage drive 614 reads from and/orwrites to removable storage unit 618 in a well-known manner.

According to some embodiments, secondary memory 610 can include othermeans, instrumentalities or other approaches for allowing computerprograms and/or other instructions and/or data to be accessed bycomputer system 600. Such means, instrumentalities or other approachescan include, for example, a removable storage unit 622 and an interface620. Examples of the removable storage unit 622 and the interface 620can include a program cartridge and cartridge interface (such as thatfound in video game devices), a removable memory chip (such as an EPROMor PROM) and associated socket, a memory stick and USB port, a memorycard and associated memory card slot, and/or any other removable storageunit and associated interface. In some embodiments, secondary memory610, removable storage unit 618, and/or removable storage unit 622 caninclude one or more of the functions described above with respect to thepreviously discussed wafer-holder structure.

Computer system 600 can further include a communication or networkinterface 624. Communication interface 624 enables computer system 600to communicate and interact with any combination of remote devices,remote networks, remote entities, etc. (individually and collectivelyreferenced by reference number 628). For example, communicationinterface 624 can allow computer system 600 to communicate with remotedevices 628 over communications path 626, which can be wired and/orwireless, and which can include any combination of LANs, WANs, theInternet, etc. Control logic and/or data can be transmitted to and fromcomputer system 600 via communication path 626.

The functions/operations in the preceding embodiments can be implementedin a wide variety of configurations and architectures. Therefore, someor all of the operations in the preceding embodiments—e.g., thefunctions of system 400 described in FIG. 4 and the method/processdescribed in FIG. 5 —can be performed in hardware, in software or both.In some embodiments, a tangible apparatus or article of manufactureincluding a tangible computer useable or readable medium having controllogic (software) stored thereon is also referred to herein as a computerprogram product or program storage device. This includes, but is notlimited to, computer system 600, main memory 608, secondary memory 610and removable storage units 618 and 622, as well as tangible articles ofmanufacture embodying any combination of the foregoing. Such controllogic, when executed by one or more data processing devices (such ascomputer system 600), causes such data processing devices to operate asdescribed herein. For example, the hardware/equipment can be connectedto or be part of element 628 (remote device(s), network(s), entity(ies)628) of computer system 600.

In some embodiments, an apparatus includes a chuck for placing an objectthereon, a gas passage extending along a periphery of an outer sidewallof the chuck and dividing the chuck into an inner portion and a sidewallportion, and a plurality of gas holes through the sidewall portion andconfigured to connect the gas passage to a gas external to the chuck.

In some embodiments, a method includes loading a wafer onto awafer-holder structure, performing one or more operations on the wafer,and forming a gas curtain that surrounds an outer sidewall of thewafer-holder structure.

In some embodiments, a system includes a chamber and a control device.The chamber can include a wafer-holder structure that includes a chuckfor placing an object thereon, and a gas passage extending along aperiphery of an outer sidewall of the chuck. The gas passage can dividethe chuck into an inner portion and a sidewall portion. The wafer-holderstructure can also include a plurality of gas holes through the sidewallportion and configured to connect to a gas external to the wafer-holderstructure to the gas passage. The gas passage can be configured to allowan inert gas to flow through the plurality of gas holes to form a gascurtain that surrounds the outer sidewall of the chuck. The controldevice can be configured to control one or more operations in thechamber and the gas curtain along the outer sidewall of the chuck.

It is to be appreciated that the Detailed Description section, and notthe Abstract of the Disclosure, is intended to be used to interpret theclaims. The Abstract of the Disclosure section may set forth one or morebut not all exemplary embodiments contemplated and thus, are notintended to be limiting to the subjoined claims.

The foregoing disclosure outlines features of several embodiments sothat those skilled in the art may better understand the aspects of thepresent disclosure. Those skilled in the art will appreciate that theymay readily use the present disclosure as a basis for designing ormodifying other processes and structures for carrying out the samepurposes and/or achieving the same advantages of the embodimentsintroduced herein. Those skilled in the art will also realize that suchequivalent constructions do not depart from the spirit and scope of thepresent disclosure, and that they may make various changes,substitutions, and alterations herein without departing from the spiritand scope of the subjoined claims.

What is claimed is:
 1. A method, comprising: forming a plasma in achamber; flowing an inert gas into a wafer-holder structure in thechamber; and outputting a portion of the inert gas from a sidewall ofthe wafer-holder structure and towards a vertical direction.
 2. Themethod of claim 1, further comprising outputting another portion of theinert gas from the sidewall of the wafer-holder structure and towards ahorizontal direction.
 3. The method of claim 1, wherein flowing theinert gas into the wafer-holder structure comprises flowing the inertgas in a horizontal portion of a gas passage in the wafer-holderstructure.
 4. The method of claim 1, further comprising forming a gascurtain between the plasma and the sidewall of the wafer-holderstructure.
 5. The method of claim 1, further comprising adjusting a flowrate of the inert gas according to a temperature of the chamber.
 6. Themethod of claim 1, further comprising adjusting a flow rate of the inertgas according to a pressure of the chamber.
 7. The method of claim 1,further comprising: loading a wafer onto the wafer-holder structure; andprocessing the wafer using the plasma.
 8. An apparatus, comprising: awafer-holder structure configured to hold a wafer and to output a gasthrough a plurality of gas holes on a sidewall of the wafer-holderstructure; a base structure connected to the wafer-holder structure; anda gas passage through the base structure and connected to the pluralityof gas holes, wherein the gas passage comprises a horizontal portion. 9.The apparatus of claim 8, wherein the plurality of gas holes areconfigured to output the gas in a horizontal direction.
 10. Theapparatus of claim 8, wherein the plurality of gas holes are configuredto output the gas in a vertical direction.
 11. The apparatus of claim 8,further comprising an inlet connected to the gas passage at a bottom ofthe base structure and configured to receive an inert gas source. 12.The apparatus of claim 8, wherein a diameter of the plurality of gasholes is in a range of about 0.05 mm to about 0.5 mm.
 13. The apparatusof claim 12, wherein the diameter is about 0.1 mm.
 14. The apparatus ofclaim 8, wherein the plurality of gas holes are distributed uniformly onthe sidewall of the wafer-holder structure.
 15. A system, comprising: achamber configured to form a plasma to process a wafer; a wafer-holderstructure, in the chamber, configured to hold the wafer and to output aninert gas through a plurality of gas holes on a sidewall of thewafer-holder structure; a base structure connected to the wafer-holderstructure; a gas passage through the base structure and connected to theplurality of gas holes; and a control device configured to control aflow rate of the inert gas in the gas passage.
 16. The system of claim15, further comprising a sensor configured to monitor a pressure of thechamber, wherein the control device is further configured to adjust theflow rate according to the pressure of the chamber.
 17. The system ofclaim 15, wherein the gas passage comprises a horizontal portion. 18.The system of claim 15, wherein the plurality of gas holes areconfigured to output the inert gas in a horizontal direction.
 19. Thesystem of claim 15, wherein the base structure comprises anotherplurality of gas holes on a sidewall of the base structure and connectedto the gas passage.
 20. The system of claim 15, further comprising aninlet connected to the gas passage at a bottom of the base structure andconfigured to receive an inert gas source.